The proposed studies are initial experiments in a program that will examine the cognitive functions of the cortical regions surrounding the posterior rhinal sulcus in the rat. These regions include the perirhinal cortex and the newly defined postrhinal cortex. The P.I was a major contributor to neuroanatomical findings that led to more precise boundaries for the rat perirhinal cortex and provided the conceptual basis for defining the rat postrhinal cortex, a region that exhibits considerable homology with the monkey parahippocampal cortex. A role in recognition memory has already been identified for the perirhinal cortex. Electrophysiological studies provide evidence that this function may be mediated by the encoding of familiarity or recency. Other work suggests that the functions of this region may not be limited to recognition memory. The planned experiments will address the hypotheses that the perirhinal cortex also supports mnemonic processes by configuring multiple stimuli to form single representations as distinct from the individual elements and by permitting the association of stimuli across sensory modalities. These hypotheses will be addressed using behavioral tasks that require the configuration of stimuli within and across sensory modalities in combination with experimental lesion studies. Performance of animals with selective perirhinal lesions will be compared to that of animals with selective lesions of the adjacent postrhinal cortex as well as to normal and operated controls. The proposed experiments w\ill employ behavioral approaches aimed at further characterizing the contribution of the perirhinal cortex to mnemonic processes and at dissociating the function of the perirhinal cortex from that of the neighboring and newly defined postrhinal cortex. This work will provide the background for continued examination of the perirhinal cortex using electrophysiological methods in combination with the same behavioral protocols. These experiments hold the potential for broadening our understanding of the perirhinal cortex by discovering a role in cognitive functions other than recognition memory or familiarity judgement. This work may also shed light on the contributions of the postrhinal cortex to cognition.